Intravascular bubbles associated with intravenous injections and altitude.

Ultrasonically detected microbubbles were more abundant in the pulmonary artery of dogs intravenously injected with 10 ml of saline than in the same noninjected controls during 10,000 ft (3,048 m), 20,000 ft (6,096 m), and 40,000 ft (12,192 m) exposures. Continuous intravenous (i.v.) drip infusions also introduced many small bubbles. Since they may serve as "nuclei" for visible intravascular bubble formation, are sometimes associated with decompression sickness, and are additionally considered undesirable, it would appear prudent to minimize i.v. injections immediately before flights. However, a 10-min delay before ascent will reduce their number and a 60-min delay will insure their almost complete absence. Also, slow ascent, a 1-h denitrogenation time, or use of a degassed solution will help reduce their total number.